The use of microstructures to assemble, fortify or dilate biological structures inside the body during and after surgery can help the surgeon in a number of ways. The operation of electrically actuated tools can help the surgeon to simultaneously position, operate manually, and observe. By positioning the tool by hand and separately operating the tool through external controls (i.e. footswitch, voice control, other software-control) a much higher degree of precision is achieved. In microsurgery, this is especially desired.
The development of microactuators has been spurred on by the desire to be able to use tools beforehand or during invasive surgical procedures. Because tools may be used for cutting, drilling, holding, dilating, suturing, adapting or supporting, the tools must have specific size and shape. For example, a certain tool might be need during a surgery and the only way to introduce this tool is to place it inside a catheter or needle. Thus, the tool must designed within the specific dimension of the catheter or needle.
The necessary elements to accomplish these functions are the electrochemically activated microactuators, built by micromachining thin metal and polymer layers or only polymer layers. (Elisabeth Smela, Olle Inganäs and Ingemar Lundström: “Controlled Folding of Micron-size Structures”, Science 268 (1995) pp. 1735-1738) or only polymer layers. These microactuators can be produced in sizes from micrometers to centimeters, and operate well in biological fluids such as blood plasma, blood, buffer and urine. They are therefore suitable tools for micro invasive surgery inside the body. The versatility of construction and the speed of response, as well as the force of these microactuators render them as one of the best types of microactuators inside the body. An international patent covers one route of fabrication of such devices (A Elisabeth Smela, Olle Inganäs and Ingemar Lundström: “Methods for the fabrication of micromachined structures and micromachined structures manufactured using such methods”, Swedish patent application number SE 9500849-6, Mar. 10, 1995 in succession also a PCT and international patent).
The combination of microactuators and catheters are not well documented in the literature. No patents describe the use of microactuators as tools housed inside a catheter; however several examples of microactuators used to position a catheter are to be found in the following patents:
U.S. Pat. No. 5,771,902 Micromachined actuators/sensors for intratubular positioning/steering
U.S. Pat. No. 5,519,749 Microvalve
WO9837S16A1 Microfabricated therapeutic actuators
WO9739688A2 Method and apparatus for delivery of an appliance in a vessel
WO9739674A1 Spring based multi-purpose medical instrument
U.S. Pat. No. 5,855,565 Cardiovascular mechanically expanding catheter
Several mechanisms are suggested for the microactuators in these applications, found among shape memory alloys (including polymeric materials) and piezoelectric materials. The use of conjugated polymers in micromuscles is not documented for catheter tools.